Efficient photocatalytic activity in the visible range has been achieved with titanium oxide thin films. Doping, induced by oxygen deficiencies, is the key to the increased photodegradation ...properties of the film as both experimental and theoretical studies of the thin films demonstrate. The Figure shows an AFM image of the surface morphology of a TiO2 layer.
Conversion of thermal radiation into electrical current in thermophotovoltaic devices is directly influenced by the heat transfer, since the cell efficiency depends on the temperature. For ...micro-scale devices, heat management is yet more important due to the proximity between the components. A detailed study in these systems needs to considers the presence of wavelength-selective optical filters, used to reflect undesired radiation. In this study, we propose a model where the dependence of the physical parameter with the radiation wavelength is taken into account through a discretization of the radiation spectrum into several bands and estimation of average values. By coupling this procedure with a computational fluid dynamics solver, the cell efficiency as a function of geometrical and operational parameters can be estimated. The results indicate the existence of an optimal emitter/cell distance, depending on the emitter temperature and the heat transfer coefficient between the cell and the external medium. A secondary cooling mechanism, the air flow between the emitter and the filter, can also help to reduce the cell temperature. While the emitter average temperature has a strong impact on the cell efficiency, the temperature distribution in the emitter surface has no significant influence, allowing the use of average values.
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•Radiation and temperature distribution significantly affect TPV systems.•Wavelength-dependence of physical properties is considered.•There is an optimal emitter/cell distance.•Airflow between the emitter and the cell acts as a secondary cooling mechanism.•Emitter temperature profile has little influence on the TPV cell efficiency.
Anatase phase of titanium oxide is the most promising photocatalyst material for organic pollutant degradation. However, due to its large band gap energy (3.2
eV) it is not viable to use sunlight as ...an energy source for the photocatalysis activation, and so, ultraviolet (UV) radiation below the wavelength of 380
nm is required.
This paper focuses on the experimental demonstration of the reduction of this large band gap energy by inducing defects in the anatase structure under the form of oxygen sub-stoichiometry. TiO
2 thin films were prepared in a metal organic chemical vapour deposition (MOCVD) reactor. The samples stoichiometry was measured by the Rutherford backscattering spectrometry (RBS) technique. Optical characterisation was also performed and the photodegradation activity in the visible range was tested using nonylphenol, which is one of the most harmful pollutants present in waste waters.
Over the past decade the increase of elderly population has determined a rise in the incidence of bone fractures, and the improvement of the implant–bone interface remains an open problem. ...Metal-organic chemical vapour deposition (MOCVD) has recently been proposed as a technique to coat orthopaedic and dental prostheses with metal nanostructured oxide films either through the decomposition of oxygenated compounds (single-source precursors) or the reaction of oxygen-free metal compounds with oxygenating agents. The present study was performed to assess the in vivo biocompatibility of commercially pure Ti (control material: TI/MA) implants (∅ 2
mm×5
mm length) coated with nanostructured TiO
2 films by MOCVD (Ti/MOCVD) and then inserted into rabbit femoral cortical (middhiaphysis) and cancellous (distal epiphysis) bone. Histomorphometric, ultrastructural and microhardness investigations were carried out. Four and 12 weeks after surgery, significant (
p<0.0005) increases in AI of Ti/MOCVD implants were observed as compared to Ti/MA implants (distal femoral epiphysis: 4 weeks=8.2%,
ns; 12 weeks=52.3%,
p<0.005; femoral diaphysis: 4 weeks=20.2%,
p<0.0005; 12 weeks=10.7%,
p<0.005). Bone microhardness results showed significant increases for the Ti/MOCVD versus Ti/MA implants at 200
μm in the femoral diaphysis (4 weeks=14.2,
p<0.005) and distal femoral epiphysis (12 weeks=14.5,
p<0.01) at 4 and 12 weeks, respectively. In conclusion, the current findings demonstrate that the nanostructured TiO
2 coating positively affects the osseointegration rate of commercially pure Ti implants and the bone mineralization at the bone–biomaterial interface in both cortical and cancellous bone.
Nine areas of the brain were studied by electron paramagnetic resonance spectroscopy and total reflection X-ray fluorescence spectroscopy to measure paramagnetic metal ions, free radicals ...(neuromelanin), and total metal content. We also determined the extent of accumulation of metal ions by melanins incubated in homogenates of a region of the brain (putamen). The electron paramagnetic resonance spectra of metal ions varied considerably among areas of the brain. There was no correlation between total content of particular metal ions (iron was especially pertinent) and the observed electron paramagnetic resonance spectra, except that the substantia nigra appeared more consistently to have a prominent g = 4 electron paramagnetic resonance signal characteristic of ferric iron in a rhombic state. Only the substantia nigra, and to a lesser extent the locus coeruleus, had a free radical signal consistent with that of neuromelanin. This signal was much more prominent in the unprocessed substantia nigra but when metal ions were removed (reducing the amount of suppression of the electron paramagnetic resonance signal of neuromelanin due to dipole-dipole broadening from nearby metal ions), the electron paramagnetic resonance spectrum of neuromelanin of the locus coeruleus increased much more than that of the substantia nigra. This suggests that the structure of the pigment may differ in these two regions.
Incubating synthetic melanins with homogenates of putamen resulted in accumulation of metal ions on the melanins with the concentrations of the three metal ions, relative to their values in the putamen, increasing by factors of 20–30 3–4 and 25–30 for iron, copper, and zinc, respectively. This suggests that the metal content of isolated neuromelanin may include metal ions which became bound to the neuromelanin during the isolation procedure.
Bent silicon crystals mounted on high-accuracy angular actuators were installed in the CERN Super Proton Synchrotron (SPS) and extensively tested to assess the feasibility of crystal-assisted ...collimation in circular hadron colliders. The adopted layout was exploited and regularly upgraded for about a decade by the UA9 Collaboration. The investigations provided the compelling evidence of a strong reduction of beam losses induced by nuclear inelastic interactions in the aligned crystals in comparison with amorphous orientation. A conceptually similar device, installed in the betatron cleaning insertion of CERN Large Hadron Collider (LHC), was operated through the complete acceleration and storage cycle and demonstrated a large reduction of the background leaking from the collimation region and radiated into the cold sections of the accelerator and the experimental detectors. The implemented layout and the relevant results of the beam tests performed in the SPS and in the LHC with stored proton and ion beams are extensively discussed.
Reaction mechanisms between platinum acetylacetonate Pt(acac)2 and O2 or water vapor to deposit nanostructured, conductive platinum thin films at 240–300 or 280–440 °C respectively, are studied to ...elucidate the effects of experimental parameters on the film microstructure and resistivity. The use of water vapor during the decomposition process of Pt(acac)2 permits slower, homogeneous film growth along the reactor. Although decomposition of Pt(acac)2 assumes different characteristics in the presence of O2 and H2O, a universal trend crystallite size–resistivity was found for almost all obtained films, representing a starting point for correlation of experimental conditions with applicative performances.
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Tissue scaffolds need to be engineered to be cell compatible, have timely biodegradable character, be functional with respect to providing niche cell support for tissue repair and ...regeneration, readily accommodate multiple cell types, and have mechanical properties that enable the simulation of the native tissue. In this study, electrospun degradable polar hydrophobic ionic polyurethane (D-PHI) scaffolds were generated in order to yield an extracellular matrix-like structure for tissue engineering applications. D-PHI oligomers were synthesized, blended with a degradable linear polycarbonate polyurethane (PCNU), and electrospun with simultaneous in situ UV cross-linking in order to generate aligned nanofibrous scaffolds in the form of elastomeric composite materials. The D-PHI/PCNU scaffold fibre morphology, cross-linking efficiency, surface nature, mechanical properties, in vivo degradation and integration, as well as in vitro cell compatibility were characterized. The results showed that D-PHI/PCNU scaffolds had a high cross-linking efficiency, stronger polar nature, and lower stiffness relative to PCNU scaffolds. In vivo, the D-PHI/PCNU scaffold degraded relatively slowly, thereby enabling new tissue time to form and yielding very good integration with the latter tissue. Based on a study with A10 vascular smooth muscle cells, the D-PHI/PCNU scaffold was able to support high cell viability, adhesion, and expression of typical smooth muscle cell markers after a 7-day culture period, which was comparable to PCNU scaffolds. These characterization results demonstrate that the unique properties of a D-PHI/PCNU scaffold, combined with the benefits of electrospinning, could allow for the generation of a tissue engineered scaffold that mimics important aspects of the native extracellular matrix and could be used for functional tissue regeneration.
Tissue engineered scaffolds should recapitulate native extracellular matrix features. This study investigates the processing of a classical polycarbonate polyurethane (PCNU) with a cross-linked and degradable ionomeric polyurethane (D-PHI), polymerized via in situ rapid light curing to yield a 3-dimensional co-electrospun nanofibre matrix with chemical diversity and low modulus character. This research advances the use of D-PHI for tissue engineering applications by providing a facile means of changing physical and chemical properties in classical PCNUs without the need to adjust spinning viscosities of the base polymer. Further, the in vivo and cell culture findings set the stage for introducing unique elastic materials which inherently support wound healing, repair, and regeneration in tissues, for applications that require the recapitulation of native extracellular matrix physical features.
Hydroprocessing catalysts based on Ni, Co, Mo and W are used in various refinery processing applications where several deactivation mechanisms become of importance (coke formation, active phase ...sintering, metals deposition, poisoning) in the catalyst's life cycle. The life cycle of commercial hydroprocessing catalysts is very complex and includes the catalyst production, sulfidation, use, oxidative regeneration followed by re-sulfidation and reuse or, if reuse is not possible, recycling or disposal. To understand the changes in catalyst properties taking place during a life cycle, the catalyst quality in the different stages can be best monitored by using advanced analytical techniques. The catalyst's life cycle is further complicated by numerous technical, environmental and organizational issues involved. In principle, different companies can be involved in each of the life cycle steps. Leading catalyst manufacturers, together with specialized firms, offer refineries a total catalyst management concept, starting with the purchase of the fresh catalyst and ending with its final recycling or disposal. Total catalyst management includes a broad range of services, ensuring optimal timing during the change-out process, reliable, smooth and safe operations, minimal downtime and maximum catalyst and unit performance.
